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Rectifier for AC stick welder..

Here are some photos of my home-made rectifier, I still have to add an inductor to smooth the ripple. I made this to add DC to my Sears Colormatic welder. I eventually plan on buying a real Tig welder, but this should help me out for the time-being.
I know spend the money on a real machine...I need to pay for my daughters first year at college and I don't want any debt, accept my mortgage...Talk to you later...

Re: Rectifier for AC stick welder..

I'm confused. I'm assuming you are taking an AC only transformer welder, passing the output thru a bridge rectifier to make pseudo DC output. I understand how you can further stabilize the output from the bridge with resistors and capacitors to create a true (flat) DC output, with resistors and large capacitors. I will note, my old Sears Craftsman / Century 1980's era transformer machine used the pseudo output for DC without further damping function. It worked okay for welding, but you could not use a DC clamping ammeter to read current flow.

So what's the inductor for? Are you attempting to create some sort of chopped output at particular frequencies?

Re: Rectifier for AC stick welder..

A low voltage transformer primary will work as an inductor,if you can find one that will handle the amperage.
Though saturability of the coring might be iffy,a simple straight Iron core may be the simplest
There were also some inductor experiments on a welding with batteries thread, and this one was fairly detailed .http://weldingweb.com/showthread.php?t=8996

Re: Rectifier for AC stick welder..

No not a real ham guy..kind of interested though...I understand most people don't mess around with stuff like this..I like to learn new things and to made due with what I have...I spent way to much money on things when I was younger...Now my wife and children come first. One day I will buy a true ac/dc power source that is constant current so I can have clean dc and ac high freq to weld aluminum, But for now scratch start tig for stainless and steel will due. I only screw around making things for around the house ,fixing my vehicles and art projects. I am not a coded welder, I work with code welders and anything that is serious I ask them to help.
Sorry for the long reply, I saw other dc conversions here and wanted to show what I did after reading their posts.

Re: Rectifier for AC stick welder..

The only way to get true dc is with a storage battery...When you convert ac to dc with a rectifier you get pulsing dc..to smooth the dc ripple you use a inductor capacitor filter ...or a large inductor..depends on how clean you want the dc. In this case just good enough...Later

Re: Rectifier for AC stick welder..

Post pics etc. I thought about doing this conversion once for my ac only machine but .. So I am following the post. There has been quite a bit on this very topic on here. and a lot about diodes and iducters ( do a search). Good luck.

Miller thunderbolt 250
Decastar 135E
Recovering tool-o-holic
ESAB OA
I have been interested or involved in Electrical, Fire Alarm, Auto, Marine, Welding, Electronics ETC to name a just a few. So YES you can own too many tools.

Re: Rectifier for AC stick welder..

Ok here we go...

The welds do not look good at all...I haven't tig welded in a very long time. I have never scratch started a tig torch untill this evening. I was also nervous because this was the smoke test for my rectifier... It worked !
Now I can start a lot of practicing !
Oh yeah, There's a picture of my folding welding table that is to heavy with a 3/8" top...I was inspired to build it from the people on this forum...When the weather here in Buffalo NY warms up a little I'll paint it...Later ...

Re: Rectifier for AC stick welder..

Here are some pictures of the rig with a manual gas solenoid. I didn't want to wait for a torch with a valve. The welds are with e3 electrodes..not thoriated electrodes. I am going to make a platform to hold the power supply and the bottle of argon...There are pictures of the shelf that will hold the rectifier...the argon bottle will be behind the power unit...later..

Re: Rectifier for AC stick welder..

Re: Rectifier for AC stick welder..

I painted the shelf and added a torch/ground hanger..I still want to build a cart to hold the machine and the bottle of argon..here is a picture of my latest weld..3/32 thoriated tungsten...I finally understant how clean metal means it is easier to start an arc....To many years using a mig welder on rusty western NY steel..Oh yeah...trying to add a post flow timer circuit too..

Re: Rectifier for AC stick welder..

Here is the beginning of the welder cart and some more welding pictures.. .100" steel to .100" chinese steel, the square I welded around..3/32" tungsten 2% thoriated, 15cfh argon, the cart I welded with my lincoln 255 power mig...later

Re: Rectifier for AC stick welder..

For an inducter I suppose you could wrap ...like 6 awg single around a ...what do they call the short weight lifting bar? maybe that would be better and help you stablize. I don't know.

Miller thunderbolt 250
Decastar 135E
Recovering tool-o-holic
ESAB OA
I have been interested or involved in Electrical, Fire Alarm, Auto, Marine, Welding, Electronics ETC to name a just a few. So YES you can own too many tools.

Re: Rectifier for AC stick welder..

I have a piece of laminated steel from an old transformer, I need to make some brackets to mount it in the bottom of the rectifier box. I also need to make some ends to keep the wire coils in place. I was excited the rectifier worked and I wanted to mess around with it,you know kid with a new toy. I'll fine tune it soon..I wanted to get better at scratch starting an arc too. Oh yeah, the arc, once started is stable. The only time I had issues was when I was in a hurry and didn't clean the base metal good enough. Bad habit from welding rusty vehicles back together with a mig. Without a sandblaster , a wire brush and grinder can only dig out so much rust.

Re: Rectifier for AC stick welder..

Yes, The diodes I had were only rated to 150 amps,I only use it on the lower output. I am going to order new diodes with a higher rating..I used 2 stud anode and 2 stud cathode..look around for the schematics if you aren't familiar with electricity..It will hurt or kill you..!

Re: Rectifier for AC stick welder..

Originally Posted by Fuelhead

Yes, The diodes I had were only rated to 150 amps,I only use it on the lower output. I am going to order new diodes with a higher rating..I used 2 stud anode and 2 stud cathode..look around for the schematics if you aren't familiar with electricity..It will hurt or kill you..!

Actually,If they are properly heat sinking,each leg only runs half of the time.
That would mean the 150a diodes should be good up to 300a.

Re: Rectifier for AC stick welder..

You know...I was thinking that, I read some other posts regarding this and that's what was stated. I never messed around with large stuff like this. I have made small power supplies to mess around with small electronic circuits, never anything of this current. When I made the copper buss bars/heat sinks I filed them flat with a vixen file and then used a whet stone to get them flat for the diodes to sit on. With this and the cooling fan I guess I can crank out the output and see how it goes! Thanks for the reminder!

Re: Rectifier for AC stick welder..

Originally Posted by Fuelhead

You know...I was thinking that, I read some other posts regarding this and that's what was stated. I never messed around with large stuff like this. I have made small power supplies to mess around with small electronic circuits, never anything of this current. When I made the copper buss bars/heat sinks I filed them flat with a vixen file and then used a whet stone to get them flat for the diodes to sit on. With this and the cooling fan I guess I can crank out the output and see how it goes! Thanks for the reminder!

Re: Rectifier for AC stick welder..

You can also make an air-core inductor, or even a sliding core. Put many turns around a pvc tube. You can find an iron bar or equivalent to go inside the pvc. Then you could run it full air core, or you could move the bar to adjust the inductance.

Capacitors are not what you want. Yes, some resistance going into a capacitor forms a low-pass filter. However, a capacitor stores charge and can release it basically as fast as its internal resistance (and inductance) will allow. This means the capacitance would charge to the OCV during times you weren't using it, then would discharge in a huge surge current during arc start, potentially blowing away whatever you are trying to weld on. A capacitor would work perfectly for CV though, but that's not what you want.